The field of art to which this invention pertains is photoreactive compositions for use in photoresist coatings.
The physical properties of photoresist coatings change when the coatings are exposed to light. The change usually is one of solubility and results in solvent discrimination between exposed and unexposed areas. Exposure of coatings to light through a pattern results in solubility changes and, therefore, image boundaries that can be used to form resist images. Images can be produced by solvent development in either negative-or positive-working modes.
The negative-working mode depends on a light induced decrease in solubility of polymer molecules. The positive-working mode is just the opposite, i.e., exposure to light makes the polymer more soluble in the solvent (developer).
Photoresist polymer compositions must fulfill a number of physical property dependent requirements under practical working conditions. The polymers must form homogeneous solutions in ecologically acceptable solvents; form smooth, flaw-free coatings with good adhesion in all process steps; be characterized by good solution stability for storage; form tack-free coatings; provide good image discrimination; resist flow or creep during processing at high temperatures; form thermally stable images that do no flow; and be removable or strippable after the required fabrication steps.
Negative acting photoresists based on polydienes cross-linked with bisazides are described in The Journal of Photographical Science, Volume 12, p 181 (1964). Photoresist systems based on poly(cis-isoprene) and bis(4-azidobenzal)cyclohexanone have been studied using infrared and ultraviolet spectroscopy, solvent extraction and thin layer chromatography as described in The Journal of the Electrochemical Society, Volume 124, p 1394 (1977).
Photoresist compositions based on poly(vinylphenols) are described in U.S. Pat. No. 3,869,292 and U.S. Pat. No. 4,439,516. Such compositions are made from poly(vinylphenols) and sensitizers, such as aromatic esters or amides of ortho-naphthoquinone diazide sulfonic or carboxylic acid.
Positive acting photoresists are described in U.S. Pat. No. 4,409,317. Such compositions contain alkali soluble resins such as poly(vinylphenol).
Photosensitive compositions made from polymers of the reaction product of p-vinylphenol and cinnamic acid chloride are described in U.S. Pat. No. 3,882,084.
Positive or negative acting photoresist compositions are described in U.S. Pat. No. 4,491,628. Such compositions are made from polymers which contain acid labile groups, such as tertiary butyl carbonates of poly(vinylphenols).
In U.S. Pat. No. 4,469,778, photosensitive compositions in which the photosensitizers are bisazide compounds are described.